If a vehicle suffers a fault, the vehicle is taken to a repair shop of a dealer or the like. The operator (technician) who is responsible for repairing the vehicle connects an electronic control unit (hereinafter referred to as “ECU”) on the vehicle to an external diagnostic apparatus, reads fault data (fault code) from the ECU, analyzes a defective location or a fault source, and makes necessary repairs or an necessary adjustment.
When vehicles are manufactured, they are checked at the final inspection stage of the production process to see if their sensors or ECUs are functioning properly or not. While vehicles to be diagnosed are conveyed one after another at the final inspection stage, each of the vehicles is controlled to operate (idle) stably and then diagnosed collectively and efficiently {see S603 in FIG. 12, [0044], and [0045] of Japanese Laid-Open Patent Publication No. 09-210870 (hereinafter referred to as “JP09-210870A”)}. According to JP09-210870A, after a cable 5 of a vehicle diagnostic apparatus 2 is connected to each of successively conveyed vehicles, the vehicle diagnostic apparatus 2 automatically starts diagnosing the vehicle without displaying a menu screen ([0035]).